A cautionary tale, Eagle SA-200 and old valve amplifiers.
Jun 26, 2021 10:57:28 GMT
Bigman80 and robbiegong like this
Post by firebottle on Jun 26, 2021 10:57:28 GMT
A very old Eagle valve amp has found its way onto the work bench. I can't find a date anywhere but the design is outdated, particularly with very sensitive inputs.
The cautionary part is not knowing what condition anything like this is going to be in. This one was well knackered, all the oil coupling caps were leaky sending all the circuit parameters way off.
The output stages were drawing way too much current, if powered for any length of time the output transformers could have been destroyed.
Unfortunately even when the components were replaced it was discovered that the design was over stressing the output valves big time, so other components needed replacement to bring the anode dissipation within acceptable levels. Pic showing the new components around one output valve socket.
All low voltage capacitors had dried out as well, fortunately all the high voltage caps checked OK. All the components changed:
However now it's working there are design issues, apart from the high sensitivity. The phono equalisation is in circuit for all inputs, how weird is that?
So unless you have the skills or know a tame EE my advice is avoid this type of 'bargain'.
The cautionary part is not knowing what condition anything like this is going to be in. This one was well knackered, all the oil coupling caps were leaky sending all the circuit parameters way off.
The output stages were drawing way too much current, if powered for any length of time the output transformers could have been destroyed.
Unfortunately even when the components were replaced it was discovered that the design was over stressing the output valves big time, so other components needed replacement to bring the anode dissipation within acceptable levels. Pic showing the new components around one output valve socket.
All low voltage capacitors had dried out as well, fortunately all the high voltage caps checked OK. All the components changed:
However now it's working there are design issues, apart from the high sensitivity. The phono equalisation is in circuit for all inputs, how weird is that?
So unless you have the skills or know a tame EE my advice is avoid this type of 'bargain'.
